Advanced wetsuits and global stoke has pushed the boundaries of surfable waters to the far corners of the globe. We are now surfing in climates that are more suited to sauna than surfing. That being said, there are probably more unsurfed waves waiting for exploration in the far reaches of the north and south of the globe than the temperate and tropical regions. The cold must be respected however, and the unprepared surfer risks injury or even death from hypothermia and or drowning.
Our Bodies Are Hot
Being warm-blooded, homeothermic dudes and dudettes, our bodies need to maintain a very narrow temperature range in order to function properly as cellular metabolism starts to malfunction at around 32O C (90O F).
The primary mechanisms of heat loss are radiation, conduction and evaporation. As surfers, our primary source of heat loss is conduction because our bodies lose heat 25 times faster in cold water than in air of the same temperature. In windy conditions evaporative heat loss is also a significant source of heat loss.
Fortunately, our bodies produce heat, primarily from our heart, liver, and muscles where most cellular metabolism takes place. Additionally the shivering reflex kicks in when we start getting cold which increases our metabolic rate up to five fold, significantly increasing heat production. Behavioral mechanisms such as putting on the appropriate wetsuit, or paddling in when we start feeling cold also play a huge role in minimizing heat loss.
They say that to diagnose a fever, you first have to take a temperature1. The same can be said for hypothermia. But where can an accurate body temperature be best measured? At face value, this question may seem simple enough, but after thinking it over, this question equates to asking where the soul of the human body resides. Many have asked this question, many have answered, and a few brave souls have had a thermometer in their rectum. So is the soul of humanity up our asses? This turns out to be not too far from the truth as the best “core” body temperature measurements are obtained from esophageal probes. An important caveat here is that most thermometers in your medicine cabinet or nursing cart are unable to measure temperatures below 32O C. For these readings, a digital probe (rectal or esophageal) must be used.
Grading of Hypothermia
The standard grading scale for hypothermia is listed below, but at the beach it is unlikely that you will have brought your rectal probe with you, so the diagnosis remains a clinical one. When surfing in colder conditions play close attention to the often-subtle physical cues listed below, before it is too late!
Mild (35O C to 32O C): At mild stages of hypothermia, our bodies are still in control. Here we see the normal physiologic effects of shivering, teeth chattering, seeking out of warmth, leg cramps, and diuresis. Fine motor skills, strength, and balance are often affected. This makes catching waves difficult. Shivering means it is time to head in.
Moderate (32O C to 28O C): At these colder temperatures, our physiologic mechanisms to regulate heat start to fall apart. Bradycardia and atrial fibrillation are common. Brain function declines so we get confused and ataxic. This author had one epic winter surf session right before a shift in the Emergency Department when walking into work, I was noticeably ataxic. So much so, that one of my colleagues was concerned that I was drunk. After explaining the situation and having a hot cup of herbal tea, the ship was righted and I saved many lives that day. It is at these temperatures that we start to see “paradoxical undressing” where we start taking our clothes off despite the cold. (For some time I have been trying to make a good “paradoxical undressing” joke and nothing good is coming to me, perhaps dear reader you could do a better job here.) At these low temperatures, shivering and therefore increased heat production stops. We are still alive, but in a perilous situation.
Severe (<28O C): Below these temperature’s our heart and brains can’t function and we see more dangerous cardiac rhythms like ventricular fibrillation and the most deadly cardiac rhythm- cardiac arrest. Patients are comatose at this temperature and all thought processes about waves and burritos have ceased.
Treatment. Just Rewarm the Dude, Duh
While it may sound simple, this can get very complex. In addition to rewarming a hypothermic patient, the provider must also consider a myriad of other concomitant issues, like trauma, airway management, CPR, frostbite and drowning.
Passive External Rewarming: While simple, this technique has some of the fastest rewarming rates at up to 2OC per hour, but relies on intact physiologic mechanisms of rewarming ie. the ability to shiver. Passive external rewarming simply consists of removal of wet clothing, warm blankets and oral warm fluids with glucose. Because it relies on our bodies’ ability to rewarm itself, it only works for mild hypothermia. Think of this as taking off a wetsuit and wrapping yourself up in a bunch of blankets, indoors and out of the wind. If shelter and warm dry clothing are not available it may be best to cover keep the wetsuit on and cover yourself or the victim with a windproof insulating layer such as a board bag.
Active External Rewarming: This technique uses heat applied externally to rewarm our little ice cube. These techniques included forced hot air, warm baths and often warmed IV fluids. These techniques are still quite simple and can be done out of the hospital setting. I would equate this with getting in your car and blasting the heat after a cold session. One quick caveat here is that rewarming patients with severe hypothermia can lead to something known as “Core Temperature Afterdrop.” This potentially fatal event happens when the body is being rewarmed and circulation of cold, acidic blood from the extremities starts to flow back to the heart. This can be avoided by rewarming the trunk first, then the extremities.
Active Internal Rewarming: Now things get really interesting. Because these techniques are invasive and carry risks, they are usually reserved for severe hypothermia or when other techniques are not working. Basically this includes warming up the inside of our surfer bodies with the goal of warming the heart and blood rapidly. For starters, warm IV fluids (40-42OC) is simple and safe. Other techniques such as thoracic lavage with warm saline can be accomplished with 2 small chest tubes. As in the picture below:
Less effective techniques are peritoneal lavage, warmed fluids in a Foley catheter, and warmed air through the ventilator.
Cardiopulmonary Bypass: In severe cases of hypothermia, or during periods of CPR Cardiopulmonary bypass or ECMO can be used with rapid rewarming rates. This technique sucks the blood from the heart, rewarms it then pumps it back to the heart. In a NEJM article from 2012, this technique was promoted as the most effective method of rewarming3. This however requires a hospital system that is set up to handle these patients and willing thoracic surgeons with perfusionists on call. Needless to say that this is reserved for large institutions. Most of the experience with this comes from places that see frequent avalanches that are close to big cities (Vancouver, Geneva). Those authotities recommend transport to centers capable of performing these procedures in severe hypothermia even while performing CPR.
Cardiac Effects
As mentioned earlier, hypothermia has some classic effects on the heart. These findings are an Osborn J wave in the EKG at moderate levels of hypothermia, slow atrial fibrillation, and ventricular tachycardia at very low temperatures. Below is a classic EKG showing the slow atrial fibrillation and the Osborn J waves.
Furthermore, the myocardium is very “irritable” at low temperatures. Much like having to work during an epic swell, any little thing can set the heart off. Practically speaking, this means not jostling a hypothermic patient around and care taking care not to irritate the heart with the guide wire when placing a central line. Roughly transferring a patient from stretcher to gurney, for example, can precipitate ventricular arrhythmias.
For this reason, it is best not to do CPR if the cardiac rhythm is a perfusing rhythm, even if you cant feel a pulse. Because the peripheral arteries are so constricted, and the blood pressure low, the heart can still generate an adequate cardiac output without a pulse. CPR should be reserved for asystole, profound bradycardia <20, pulseless ventricular tachycardia and ventricular fibrillation.
CPR: You’re Not Dead Until You’re Warm and Dead
Given the fact that hypothermia protects the brains during periods of hypoxia and cardiac arrest, there have been cases of complete neurologic recovery after prolonged periods of cardiac arrest. The longest reported in the literature was a cardiac arrest of 190 minutes4! Because of this fact in cases of cardiac arrest, prolonged CPR is often indicated until a patient can be either rewarmed or transported to a center where cardiac bypass or ECMO can be performed.
Before discussing this, however, it is best to talk about who not to do CPR on and to call it a day. People have talked about futility in resuscitation when the serum potassium level is above 12, when the airway is packed with snow or ice, or when the body is encrusted with ice.
If there are still no pulse or signs of life after rewarming to 32OC, that’s when you can call it a day and let all his buddies know that there will be a memorial paddle out at his favorite spot.
Surfer’s Tips
Those of us that have surfed cold water for many years have all come up with tricks to prolong a session and cheat death for a little longer. Here are my tips:
- Know your limits, get out of the water when you are starting to get cold, leg cramps or can’t feel your fingers.
- Stay in shape. Paddling in a 6mm wetsuit is exhausting. If you are not surfing regularly in the winter, stay in shape by hitting the pool.
- Get a good wetsuit without holes. One little hole will render a wetsuit much less effective.
- Get hot before getting in the water. Crank the heat in the car, drink warm sugary fluids, try not to get out of the car for too long while checking the surf.
- Warm up some Gatorade and drink this on the way to the surf.
- Change in your car, or even better, get in your wetsuit at home and drive to the surf in your suit. Just don’t pee.
- Stay active in the water. Our bodies generate more heat while paddling than sitting.
- Keep your car keys accessible. You learn the hard way that your hands don’t work well when they are cold and you don’t have the dexterity to get out your car key from a zany wetsuit key holder and open your car door.
- A Thermos of warm water poured over your head after a sesh is almost as cathartic as peeing in your wetsuit.
Bibliography
1. Shem S. The House of God.
2. Danzl D, Pozos R. Accidental hypothermia. N Engl J Med. 1994;367(20):1930–8. doi:10.1056/NEJMra1114208.
3. Brown DJA, Brugger H, Boyd J, Paal P. Accidental Hypothermia. N Engl J Med. 2012;367(20):1930–1938. doi:10.1056/NEJMra1114208.
4. Husby P, Andersen KS, Owen-Falkenberg A, Steien E, Solheim J. Accidental hypothermia with cardiac arrest: Complete recovery after prolonged resuscitation and rewarming by extracorporeal circulation. Intensive Care Med. 1990;16(1):69–72. doi:10.1007/BF01706328.